Abstract

Wagnerite (Mg,Fe,Ca,Mn)2[PO4(F,OH)] was found in high-MgAl granulite near Anakapalle, ca. 40 km W of Vishakhapatnam, East-India. This is the first reported occurrence of this mineral in the granulite-facies Eastern Ghats Belt (EGB). The high-MgAl granulite occurs as xenoliths of several meters in diameter within basic granulite. The rocks experienced Grenvillian ultra-high-temperature (UHT) metamorphism (8 kbar; T > 900°C). Still at high-grade conditions, the rock assemblage was intruded by large volumes of felsic melt (charnockite). Hence, the MgAl granulite became partially metasomatised, resulting in microdomains with variable Ca/(Ca+Mg) - ratios and different assemblages. Three principal wagnerite-bearing petrographic domains are distinguished. Within domains 1 & 2 (Ca/(Ca+Mg) ~ 0.02) wagnerite occurs as a stable phase of the UHT-assemblage and is the major phosphorus-bearing phase, while apatite is absent. In domain 3 (Ca/(Ca+Mg) ~ 0.25), wagnerite reacted with the intruding felsic melt and is now rimmed by apatite. Isokite, CaMg[PO4F], was not observed and seems not to be stable at UHT-conditions.